Tab. REF (a) assumes a nonuniform source input bit sequence \(S=[S_1 S_2]\)  with a fixed length \(k=2\) . The bit sequence conversion is given by Huffman coding [1]}, which allocates a short output string to a high probability input word. The output bit sequence \(C\)  have variable lengths \(n_{C}\)  from 1 to 3 in this example. Then the fixed input length \(k=2\)  is shortened to \(n_{\mathrm {avg}}=\mathbb {E}[n_{C}]=1.7\)  on average, where \(\mathbb {E}\)  denotes expectation. Such conversion is useful to reduce the required storage size after conversion. Huffman coding is an invertible data compression; however, it is usually not suitable for high throughput data communications due to issues of latency and required storage size in the variable-length conversion process.
